1. Field of the Invention
The present invention relates to a servo system and method, more particularly, the present invention relates to hybrid linear/rotary fast servo systems and methods to enable, for example, fabrication of complex three-dimensional surface features on a variety of components, and steering a light beam in an optical system.
2. Description of Related Art
A fast tool servo is a well-known device that can be added to a new or existing machine tool to provide an additional axis of motion between the cutting tool and a workpiece. A fast tool servo most notably distinguishes itself by its ability to move the tool at a much higher bandwidth that is at a high speed of controlled, repetitive motion, on its axis relative to the other machine tool axes, with accuracy equal to or better than that of the other tool axes. Fast tool servos fall into two broad categories: rotary and linear. A rotary fast tool servo produces relative motion between the cutting tool and a workpiece by rotation of a swing arm that carries the tool at a fixed radius from the axis of rotation. A linear fast tool servo produces relative motion between the cutting tool and a workpiece by producing a linear translation of the tool. A steering mirror is a well-known device that can be added to an optical system to allow deflecting an electromagnetic beam.
Background information on a rotary fast tool servo system is described in U.S. Patent Application Publication No. 2005/0166726 A1, entitled “Rotary Fast Tool Servo System and Methods,” to Montesanti et al., published Aug. 4, 2005, including the following: “The present invention is directed to a rotary fast tool servo system that improves the accuracy and speed to enable and meet manufacturing goals for, for example, fabricating three-dimensional surface features . . . . In a preferred embodiment, the rotary fast tool servo system includes a cutting element mounted to a rotating arm that is driven by an actuator. The arm is mounted to the fast tool servo base by flexures on at least one side of the cutting element. Each flexure preferably includes orthogonally positioned flexure elements that extend from the rotating arm to the base. The rotating arm can be oriented vertically, horizontally, or in any other desired orientation.”
Background information on a fast tool servo system having linear or rotational movement about a single axis is described in U.S. Patent Application Publication No. US2005/0056125 A1, entitled “Flux-biased electromagnetic fast tool servo systems and methods,” to David L. Trumper, published Mar. 17, 2005, including the following: “The movement of the tool servo can be constrained in translation (linear FTS) or in rotation (rotary FTS) by any of the bearing technologies used in precision motion control systems. These include flexures, rolling element bearings, air bearings, hydrostatic bearings, or magnetic bearings.”
Further background information on a fast tool servo system having linear or rotational movement about a single axis is described in U.S. Patent Application Publication No. US2005/0223858 A1, entitled “Variable reluctance Fast Positioning System and Methods,” to Lu et al., published Oct. 18, 2005, published Mar. 17, 2005, including the following: “A linear fast motor 682 as described herein is used to position article 686 along a longitudinal (X) axis. Alternatively, a rotary fast motor 684 is used to rotate article 686 around axis through angle 0.”
Background information on a magnetic bearing system arranged for tilt and tip movement, in addition linear movement about a defined plane, is described in U.S. Pat. No. 4,634,191, entitled “Radial and Torsionally Controlled Magnetic Bearing,” to Studer, patented Jan. 6, 1987, including the following: “A magnetic bearing including a circular stator member having a plurality of circumferential pole faces and a suspended annular ring member with corresponding number of inward facing circumferential pole faces separated by respective air gaps. A source of DC magnetic flux circulates flux between the circumferential pole faces of the stator and the ring to provide axial stability along a central longitudinal axis. Flux coil means are included on the stator member for providing variable flux density along predetermined radial paths to provide active radial stabilization. Additionally, flux coil means are included on the stator to actively modulate the magnitude of the magnetic forces as well as their direction of differential flux control involving the DC magnetic flux to produce torquing moments about a pair of mutually orthogonal axes which are perpendicular to the central axis.
A need exists for new and/or improved flux-biased variable reluctance actuators that can provide simultaneous rotary motion or rotary and linear motion. Such a system and method of the present invention is directed to such a need.